The U.S. Department of Defense has decided to go with the flow and has elevated peacekeeping to an equal status with fighting conventional wars. This new policy is basically recognition of the fact that most of the U.S. Army has been in peacekeeping mode since the 2003 invasion of Iraq. Special training programs, and training centers, have been established to support operations in Iraq, and all this new stuff is basically for peacekeeping. The U.S. Army of today is a formidable force, but all the troops do, and train for, is peacekeeping. As late as 2004, the army spoke of maintaining the conventional war fighting skills of the troops, but this has basically been dropped. It's more important to maintain and improve peacekeeping skills. As a practical matter, the infantry have better fighting skills than ever, because they still practice a lot of infantry fighting methods as part of their peacekeeping work. But tank and artillery units would require additional training to get them back in shape for fighting a conventional war. Many tank and infantry troops have been retrained to perform infantry and peacekeeping duties.
Since the only conventional war threat the U.S. faces at the moment is a North Korean invasion of South Korea, all of this peacekeeping stuff is not a major problem. North Korean tanks and artillery are ancient, and their troops have not been able to train as much as they used to because of over a decade of poor economic conditions in the country, including years of famine. Discipline and readiness in the North Korean military has also been declining. But the last of convention war training for U.S. troops would cost more American casualties if these peacekeeping divisions were suddenly shipped off to South Korea to deal with a North Korean invasion. However, the current plan is to provide the South Koreans with a lot of American air power, and hope that the South Korean forces could handle the North Koreans. This is not unreasonable, but the North Koreans might use chemical weapons, and the situation in South Korea could get nasty.